A New Hampshire fireworks store has told the FBI that it sold four-hundred dollars worth of fireworks in February to accused Boston bomber Tamerlan Tsarnaev.

The gunpowder in fireworks is often used in bombs.

"He just wanted the biggest, loudest stuff we had in the store," said Megan Kearns, the assistant manager of Phantom Fireworks, in an interview with ABC News affiliate WMUR.

Kearns said Tsarnaev -- the older of the two brothers now accused in the blast -- bought two large reloadable mortar kits during a two for one sale. She said she remembered Tamerlan because of his Russia accent. The store has since confirmed his purchase with store records.

"Pretty much the only thing that was remarkable about him was that he had a Russian accent, which we don't get too many people in here who have Russian accents," she said.

The amount of gunpowder that could be harvested from the kits—less than half a pound—would not have been enough to detonate the Boston bombs, Phantom Fireworks VP William Weimer said.

Fireworks have often been used by terrorists to power their bombs, including by the man who tried but failed to detonate a car bomb in Times Square. He bought fireworks from a different Phantom Fireworks store, in Pennsylvania.

"Fireworks will give you what you need in terms of blast," said Kevin Barry, Retired Detective First Grade, NYPD Bomb Squad.

Barry told ABC News that while the ingredients are easily purchased – the actual assembly instructions are still hard to find and follow.

"What it seems they did was purchased commercially manufactured mortars, ripped them down and ripped out the powder," he said. "When you confine this powder in a pressure cooker it is very powerful."

The charging document filed in the case against 19-year-old Dzhokhar Tsarnaev also notes that FBI agents found "a large pyrotechnic" in his college dorm room.

Federal agents have analyzed the two pressure cooker bombs used in the Boston Marathon attack and confirmed early speculation that the other components were also built largely, if not entirely of commercially available items, including parts of a remote control toy car, BBs and small nails.